AN955 VF Control of 3-Phase Induction Motor Using Space Vector Modulation Author: Rakesh Parekh Microchip Technology Inc. INTRODUCTION VF control using the Sine PWM algorithm is a popular algorithm for AC induction motor control; however, this algorithm has certain drawbacks which affect the overall system efficiency. A more advanced switching algorithm, like Space Vector Modulation (SVM), overcomes the drawbacks of the Sine PWM algorithm and increases the overall system efficiency. This application note includes the description of the SVM theory and its advantages over the Sine PWM. It also discusses the SVM digital implementation for VF control using Microchip’s PIC18FXX31 8-bit microcontrollers. See the “References” section for more information on AC induction motors and their control. SPACE VECTOR MODULATION (SVM) The SVM is a sophisticated, averaging algorithm which gives 15% more voltage output compared to the Sine PWM algorithm, thereby increasing the VDC utilization. It also minimizes the THD as well as switching loss. Like Sine PWM, the SVM is also a scalar control. The direct controlled variables are the motor voltage and the motor frequency. The 3-phase line-to-neutral sine waves required for driving the 3-phase AC induction motor can be represented as 120° phase-shifted vectors (VRN, VYN, and VBN) in space, as shown in Figure 1. FIGURE 1: 3-PHASE VOLTAGE VECTORS AND THE RESULTANT SPACE REFERENCE VECTOR VYN SINE PWM Traditionally, VF control using the Sine PWM algorithm is implemented using a Voltage Source Inverter (VSI) controlled by a programmable device (microcontroller or DSP). Its popularity is mainly due to its easy implementation and minimum online computational requirement. However, this algorithm has the following drawbacks: • The Sine PWM algorithm is unable to fully utilize the available DC bus supply voltage (VDC) to the VSI. The generated line-to-line voltage is less than 90% of VDC in the linear operating region. See Appendix B: “Sine PWM” for more information. • This algorithm gives more Total Harmonic Distortion (THD). • Often, to reduce run-time processing load for slow controllers, three 120° phase-shifted sine tables are created in the controller memory. This is an inefficient usage of the controller memory. • There is no degree of freedom in implementation. • This algorithm does not facilitate more advanced vector control implementation. © 2005 Microchip Technology Inc. 120° VS 120° VRN 120° VBN For a balanced 3-phase system, these vectors sum to zero. Therefore, they can be expressed as a single space reference vector (VS). By controlling the amplitude and the frequency of VS, the motor voltage and the motor frequency can be controlled. Hence, this algorithm is known as the SVM. DS00955A-page 1 AN955 A typical block diagram of a VSI controlled by the PIC18FXX31, which implements SVM, is shown in Figure 2. Point 0 is the midpoint of VDC (sometimes called the Virtual Neutral Point). For safe operation of the VSI, whenever one switch of a half bridge (Q1) is on, the other switch of the same half bridge (Q0) should be off and vice versa. This gives rise to eight distinct switching states of the VSI. Table 1 lists all the possible VSI switching states and respective line-to-neutral voltages. States 1 through 6 are called the active states, as the energy is supplied from the supply to the motor during these states. States 0 and 7 are called the inactive states, as no energy is supplied from the supply to the motor during these states. Each state can be represented as a voltage vector in space. Figure 3 shows the space vector representation of all the possible switching states. BLOCK DIAGRAM OF PICmicro® MCU-CONTROLLED VSI FIGURE 2: Q1 Q3 Q5 3-Phase ACIM PIC18FXX31 PWM0 (Q0) VDC/2 PWM1 (Q1) PWM2 (Q2) VDC O B Y N R PWM3 (Q3) PWM4 (Q4) Rectifier 115/230 VAC 50/60 Hz TABLE 1: PWM5 (Q5) VDC/2 Q0 Q2 Q4 VSI SWITCHING STATES AND RESPECTIVE LINE TO NEUTRAL VOLTAGES Switching State On Switches VRN VYN VBN Space Voltage Vector 0 Q0, Q2, Q4 0 0 0 V0 1 Q1, Q2, Q4 2/3 VDC -1/3 VDC -1/3 VDC V1 2 Q1, Q3, Q4 1/3 VDC 1/3 VDC -2/3 VDC V2 3 Q0, Q3, Q4 -1/3 VDC 2/3 VDC -1/3 VDC V3 4 Q0, Q3, Q5 -2/3 VDC 1/3 VDC 1/3 VDC V4 5 Q0, Q2, Q5 -1/3 VDC -1/3 VDC 2/3 VDC V5 6 Q1, Q2, Q5 1/3 VDC -2/3 VDC 1/3 VDC V6 7 Q1, Q3, Q5 0 0 0 V7 DS00955A-page 2 © 2005 Microchip Technology Inc. AN955 As seen in Figure 3, the entire space is distinctively divided into six equal sized sectors of 60°. Each sector is bounded by two active vectors. V0 and V7 are the voltage vectors with zero amplitude and are located at the hexagon origin. this algorithm generates maximum THD. Also, the lineto-line and the line-to-neutral waveforms are not sine waves. SVM Switching Rules VS is the resultant output due to the switching states of the VSI. For digital implementation of SVM, the VSI is switched at a very high frequency (FPWM). This frequency is high enough (>20 kHz) so as not to generate audible noise due to switching. FPWM decides the sample time TS for VS, where TS = 1/FPWM. There are various switching ways to generate VS from V0, V1...V7. Mathematically, it can be represented as shown in Equation 1. Variables T0, T1…T7 in Equation 1 are on time for the corresponding VSI states and TS is the sample time. To implement the SVM algorithm, the following switching rules are implemented: • • • • These rules help in limiting the number of switching actions and hence, there is a reduction in the switching losses. Also, they maintain symmetry in switching waveforms at the VSI output to achieve the lower THD. The SVM algorithm implementation, using these switching rules, is called Conventional SVM. When the VSI follows the switching state pattern, 1-2-3-4-5-6-1-2..., it is called the Six-Step PWM algorithm. This algorithm is easier to implement compared to all the other control algorithms. It can generate the line-to-line fundamental voltage more than the VDC. But FIGURE 3: The trajectory of VS should be a circle. Only one switching per state transition. Not more than three switchings in one TS. The final state of one sample must be the initial state of the next sample. SPACE VECTOR HEXAGON Sector 2 (Q0, Q3, Q4) V3 V2 (Q1, Q3, Q4) VS Sector 3 Sector 1 TB V7 0 (Q0, Q3, Q5) V4 Ψ V1 (Q1, Q2, Q4) TA V0 Sector 6 Sector 4 (Q0, Q2, Q5) V5 Sector 5 V6 (Q1, Q2, Q5) EQUATION 1: ⎛T0 ⎞ ⎛T1 ⎞ ⎛T2 ⎞ ⎛T3 ⎞ ⎛T4 ⎞ ⎛T5 ⎞ ⎛T6 ⎞ ⎛T7 ⎞ VS = ⎜ × V0⎟ + ⎜ × V1⎟ + ⎜ × V2⎟ + ⎜ × V3⎟ + ⎜ × V4⎟ + ⎜ × V5⎟ + ⎜ × V6⎟ + ⎜ × V7⎟ ⎝TS ⎠ ⎝TS ⎠ ⎝TS ⎠ ⎝TS ⎠ ⎝TS ⎠ ⎝TS ⎠ ⎝TS ⎠ ⎝TS ⎠ TS = T0 + T1 + T2 + T3 + T4 + T5 + T6 + T7 © 2005 Microchip Technology Inc. DS00955A-page 3 AN955 Different SVM Algorithms There are various ways to implement the SVM, such as: • • • • Conventional SVM Basic Bus Clamping SVM Boundary Sampling SVM Asymmetric Zero-Changing SVM, etc. EQUATION 3: All SVM algorithms have the same on time for active as well as inactive vectors. They differ mainly in the implementation of the inactive vectors, such as T0 and/or T7 distribution within TS. Discussion of the various other SVM algorithms is beyond the scope of this application note. Time Calculation to Generate VS Let us take an example where VS is in Sector 1 at a vector angle (Ψ), as shown in Figure 4. FIGURE 4: VECTOR VS IN SECTOR 1 Y Axis TS = TA + TB + T0/7 The time intervals, TA, TB and T0/7, have to be calculated such that the average volt seconds produced by the vectors, V1, V2 and V0/7 along the X and Y axes, are the same as those produced by the desired reference space vector VS. The modulation index or amplitude ratio is defined as: m= ⎪VS⎪ VDC where |VS| is the amplitude or the length of VS. Resolving VS along the X and Y axes, we get: EQUATION 4: V2 (VDC × TA) + (VDC × cosπ/3 × TB) = ⎪VS⎪ × cosψ × TS and VDC × sinπ/3 × TB = ⎪VS⎪ × sinψ × TS VS V0/7 Equation 2 means that the VSI is in active state 1 for TA time and it is in active state 2 for TB time. For the remaining time of TS, no voltage is applied. This can be achieved by applying inactive state 0 (or 7) for the remaining time T0 (or T7). ψ TA π/3 Solving for TA and TB, we get: TB V1 X Axis VDC It is assumed that during time TS, VS remains steady. For implementing the conventional SVM using SVM switching rules, VS is split as shown in Equation 2. EQUATION 2: ⎛TA ⎞ ⎛TB ⎞ ⎛T0/7 ⎞ VS = ⎜ × V1⎟ + ⎜ × V2⎟ + ⎜ × V0/7⎟ ⎝TS ⎠ ⎝TS ⎠ ⎝ TS ⎠ DS00955A-page 4 EQUATION 5: ⎞ TA 2 × m × sin ⎛π = ⎜3 – ψ⎟ TS √3 ⎝ ⎠ TB 2 × m × sinψ = TS √3 T0/7 can be found from Equation 3. For better THD, T0 (or T7) is split into two and then applied at the beginning and at the end of the TS. The typical VSI switching waveforms in Sector 1, as defined by Equation 2, Equation 3 and the switching rules for the conventional SVM using center aligned PWM, are as given in Figure 5. © 2005 Microchip Technology Inc. AN955 FIGURE 5: TYPICAL VSI SWITCHING WAVEFORMS IN SECTOR 1 TS T0/2 TA TS TB T7/2 T7/2 TB TS TA T0/2 T0/2 TA TS TB T7/2 T7/2 TB TA T0/2 Q1 Q0 Q3 Q2 Q5 Q4 Axes of Symmetry We can observe the different axes of symmetry in all the waveforms as shown in Figure 5. These symmetries are mainly responsible for having lower THD in SVM compared to Sine PWM in the linear operating region. From Figure 3, it is clear that in the linear operating region, the maximum line-to-line voltage amplitude can be achieved when VS is rotated along the largest inscribed circle in the space vector hexagon. In mathematical terms, this is equivalent to: EQUATION 6: mmax = Radius of Largest Inscribed Circle VDC From Figure 4 and Equation 6, it is also clear that: By solving Equation 2, Equation 5 and Equation 7, we get: EQUATION 8: Maximum Line-to-Line Voltage = 2 × mmax × VDC √3 = √3 2 × VDC = VDC × 2 √3 Equation 8 shows that it is possible to get line-to-line voltage amplitude as high as VDC using the SVM algorithm in the linear operating range. This is the main advantage of the SVM algorithm when compared to the Sine PWM algorithm. Due to higher line-to-line voltage amplitude, the torque generated by the motor is higher. This results in better dynamic response of the motor. EQUATION 7: mmax = VDC × cosπ/6 √3 = cosπ/6 = 2 VDC © 2005 Microchip Technology Inc. DS00955A-page 5 AN955 The reason for the higher line-to-line voltage in SVM can be explained with the help of Figure 6. It shows the phase voltage (line-to-virtual neutral point) generated by Sine PWM and SVM. For clarity, only two phase voltages (RO and YO) and their resultant line-to-line voltage (RY) are shown in each figure. The Sine PWM generated phase voltages are sine waves. With 120° phase shift between them, the resultant line-to-line voltage is approximately 86.6% of VDC. But, the SVM generated phase voltages have a third FIGURE 6: harmonic component superimposed on the fundamental component. The addition of this harmonic component is due to the effective usage of inactive states which is not possible in the Sine PWM. With 120° phase shift between them, the third harmonic component is cancelled out in the resultant line-to-line voltage in such a way that the resultant line-to-line voltage is boosted to VDC (100%). Thus, SVM generates line-to-line voltage with higher amplitude (about 15% more) compared to Sine PWM. GENERATED PHASE VOLTAGES AND CORRESPONDING LINE-TO-LINE VOLTAGE IN (A) SINE PWM AND (B) SVM A) Sine PWM Generated Waveforms B) SVM Generated Waveforms DS00955A-page 6 © 2005 Microchip Technology Inc. AN955 Advantages of SVM The advantages of SVM vis-a-vis Sine PWM are as follows: • Line-to-line voltage amplitude can be as high as VDC. Thus, 100% VDC utilization is possible in the linear operating region. • In the linear operating range, modulation index range is 0.0 to 1.0 in the Sine PWM; whereas in the SVM, it is 0 to 0.866. Line-to-line voltage amplitude is 15% more in the SVM with the modulation index = 0.866, compared to the Sine PWM with the modulation index = 1. Hence, it has the better usage of the modulation index depth. • With the increased output voltage, the user can design the motor control system with reduced current rating, keeping the horsepower rating the same. The reduced current helps to reduce inherent conduction loss of the VSI. • Only one reference space vector is controlled to generate 3-phase sine waves. • Implementation of the switching rules gives less THD and less switching loss. • Flexibility to select inactive states and their distribution in switching time periods gives two degrees of freedom. • As the reference space vector is a two-dimensional quantity, it is feasible to implement more advanced vector control using SVM. HARDWARE USED FOR SVM IMPLEMENTATION A PICDEM™ MC Development Board is used to develop and test the SVM control firmware. The PICDEM MC has a single-phase diode bridge rectifier, converting AC input to DC and a power capacitor bank that keeps the DC bus stable. A 3-phase IGBT-based inverter bridge is used to control the output voltage from the DC bus. See Appendix A: “PICDEM™ MC Board Technical Information” for schematics of the PICDEM™ MC Development Board. The control circuit and power circuits are optically isolated with respect to each other. An on-board flyback power supply generates +5 VD, with respect to the digital ground used for powering up the control circuit, including the PICmicro® device. The +5 VA and +15 VA are generated with respect to the power ground (negative of DC bus). The feedback interface circuit is powered by the +5 VA, while the +15 VA supplies power to the IGBT drivers located inside the Integrated Power Module (IPM). With optical isolation between the power and the control circuits, the programming and debugging tools can be plugged into the development board when main power is connected to the board. The board communicates with a host PC over a serial port configured with an onchip Enhanced USART (EUSART). The on-board user interface has two toggle switches, a potentiometer and four LEDs for indication. In this application note, switch SW1 is used to toggle between the motor Run and Stop and SW2 is used to toggle the motor rotation direction. A potentiometer is used to set the speed reference as well as the modulation index. The LEDs are used for indication of different states of control. © 2005 Microchip Technology Inc. DS00955A-page 7 AN955 DIGITAL IMPLEMENTATION To implement the SVM in the digital domain, the power control PWM module of the PIC18FXX31 is utilized. The module provides up to 8 PWM output channels with the dedicated PWM timer as its time base. The module has the capability to generate center aligned PWM with 14-bit resolution. This is the most important feature required for the SVM implementation. VS needs to be created and rotated in space for SVM implementation. To approximate the position of VS, Equation 3, Equation 5 and the previously mentioned switching rules are utilized. Looking at Equation 5, one will notice that in the same sector, TA and TB are inverted with respect to each other. Hence, only one look-up table with time entries is needed. A look-up table with TB entries (TABLE_TB_COUNT<MSB:LSB>) is created. The size of the look-up table is decided by the angle resolution used. The total sector angle is 60° (π/3 radians). To get a good resolution with an 8-bit microcontroller like the PIC18FXX31, the entire sector is divided into 256 points, giving an angle resolution of 0.234°. The center aligned PWM is used for better THD (FPWM = 1/2 * TS). The required motor speed in Hz is decided by the rate at which the VS is rotated. For this purpose, it is necessary to find both the vector angle and the vector update step size. To speed up the online calculations, the constant, DEGREE_CONSTANT, is defined; this is then used to calculate the vector update step size and the vector angle as shown in Equation 9. Looking at the definition of DEGREE_CONSTANT, one will notice that its value, without any multiplication factor, will result in a fractional number less than unity for FPWM > 1.536 kHz. Almost all motor control applications have FPWM much higher than 1.536 kHz. Handling a fractional number with any 8-bit microcontroller will require more CPU processing time. This requirement is difficult to meet in the SVM implementation, where VS is updated at every TPWM (= 1/FPWM) time interval. At the same time, the multiplication factor value needs to be such that its post-calculation adjustment requires the least possible microcontroller processing time. It is proposed that the multiplication factor be 256. This will result in a 16-bit value for the vector update step size and hence, 16-bit vector angle pointer (VECTOR_ANGLE<MSB:LSB>). As an adjustment for the multiplication factor, VECTOR_ANGLE_LSB is discarded. VECTOR_ANGLE_MSB is used as the table pointer for reading the value of TA and TB from the lookup table. Whenever a carry is generated due to the Equation 9 addition, it physically means that the VS has advanced to the next sector and hence, the sector count (SECTOR_NO) is incremented by one. The motor voltage is decided by the amplitude of VS (modulation index m). To implement the same digitally, values of TA and TB are multiplied by m. Based on TS, TA and TB, the duty cycle values for all 3 phases (R, Y and B) are calculated as shown in Table 2. Equations shown in Table 2 for Sector 1 are evident in Figure 5. Similarly, equations for other sectors are derived with the switching rule constraints. EQUATION 9: DEGREE_CONSTANT = 360 × 256 × Multiplication Factor 60 × FPWM Vector Update Step Size = DEGREE_CONSTANT × Required Motor Speed (Hz) Vector Angle = Vector Angle + Vector Update Step Size DUTY CYCLE VALUES FOR THE THREE MOTOR PHASES BASED ON VS LOCATION TABLE 2: Sector No. Phase R Duty Cycle Phase Y Duty Cycle Phase B Duty Cycle 1 T0/2 T0/2 + TA TS – T0/2 2 T0/2 + TB T0/2 TS – T0/2 3 TS – T0/2 T0/2 T0/2 + TA 4 TS – T0/2 T0/2 + TB T0/2 5 T0/2 + TA TS – T0/2 T0/2 6 T0/2 TS – T0/2 T0/2 + TB DS00955A-page 8 © 2005 Microchip Technology Inc. AN955 SVM CONTROL FIRMWARE The firmware is developed using PIC18F4431 and it implements the VF control using the SVM algorithm. Apart from the basic SVM control, the firmware incorporates various control and protection routines, such as overcurrent protection, overvoltage protection, overtemperature protection, acceleration and deceleration routine and rotation direction reversal. To implement the VF control, an analog potentiometer (R44) connected to RA1/AN1 is read. Using the CONVERT_MANUAL_COUNT_TO_HZ routine, the potentiometer setting is converted to the required motor speed in Hz. The potentiometer setting is also interpreted as the modulation index, m. To get the required motor speed, the vector update step size is calculated by calling the CALCULATE_UPDATE_STEP_SIZE routine. As described in the previous section, TA and TB values are scaled with m. All protection routines (overcurrent, overvoltage and overtemperature) are checked at a fixed time interval (presently, 5 ms set by overflow rate of the Timer1). The acceleration and deceleration routine is called at one-second intervals. Overcurrent Protection A shunt resistor (R110) in the negative DC bus gives a voltage corresponding to the current flowing into the motor winding. This voltage is amplified and compared with a reference. The current comparison setting allows a current up to 6.3A. If the current exceeds 6.3A, the FAULTA pin goes low, indicating the overcurrent Fault. The firmware is configured in the Cycle-by-Cycle Fault mode. When the Fault persists for more than a preprogrammed count (MAX_FLTA_COUNT) in the fixed time interval, then the motor is stopped and the Fault is indicated by the blinking LED1. Overvoltage Protection The DC bus voltage is attenuated using potential dividers and compared with a fixed reference. If the jumper JP5 is open, the reference is set for 200V on the DC bus. If jumper JP5 is shorted, the reference is set for 400V. The FAULTB pin is used to monitor the overvoltage Fault. If the overvoltage Fault persists for more than a preprogrammed count (MAX_FLTB_COUNT) in the fixed time interval, then the motor is stopped and the Fault is indicated by the blinking LED2. Overtemperature Protection The power module has an NTC thermal sensor, outputting 3.3V at 110°C on the junction of IGBTs. The NTC output is connected to AN8 through an optocoupler. The temperature is continuously measured and if it exceeds 110°C (MAX_JUNCTION_TEMP) for more than © 2005 Microchip Technology Inc. a preprogrammed count (MAX_TEMP_FILT_COUNT), then the motor is stopped and the overtemperature Fault is indicated by the blinking LED3. Whenever the motor is stopped due to any of the above mentioned Faults, it can be restarted by removing the Fault condition and then by pressing either SW1 or SW2. Acceleration and Deceleration The RAMP_SPEED routine is called every 1 second to implement the acceleration and deceleration feature. Both the acceleration and deceleration rates are userselectable and are given in the form of Hz/s.The acceleration and deceleration features are active only when the motor is in run condition. SOURCE CODE FILES The entire source code can be downloaded from Microchip’s web site, www.microchip.com. It includes the following files: • ...\SVM\ACSVM_OL.asm This file is located in the source code folder (Main Routine section). • ...\SVM\ACSVM_OL_routines.asm This file is located in the source code folder (Control Routine section). • ...\SVM\TIME_TABLE.asm This file is located in the source code folder (Look-up Table for TB). • ...\SVM\InterfaceACSVMConstant.inc This file is located in the source code folder (System Parameters and User-Defined Constants section). • ...\SVM\InterfaceACSVMVar.inc This file is located in the source code folder (User-Defined Variable section). An Excel file (PARAMETERS.xls) is included in the source code folder which has two worksheets. The TB_TABLE worksheet calculates TB entries based on the main oscillator frequency (FOSC), FPWM, the required dead time, etc. The LIST worksheet creates a table to be stored in the data EEPROM of the PIC18FXX31 device. This table contains all userselectable compile-time parameters, such as the motor rated speed in Hz, FPWM in kHz, the required dead time in μs, etc. The user should make sure that the table is entered in the ACSVM_OL.asm file as shown in the worksheet. An overview of the firmware’s logic flow is provided in Figure 7 and Figure 8. A complete list of system parameters and user-defined functions is provided in Table 3 through Table 5. DS00955A-page 9 AN955 FIGURE 7: SVM IMPLEMENTATION FLOWCHART (MAIN ROUTINE) Main Routine START Motor Parameters and On-Chip Peripherals Initialization Blink all LEDs at a Rate Set by the Potentiometer No Is SW1/SW2 pressed? Yes Configure PCPWM Module and Set Default Rotation Direction Call KEY_CHECK to Determine Pressed Key Call PROCESS_KEY_PRESSED to Act on the Pressed Key Has TMR1 overflowed? No Yes Call FAULT_CHECK to Check for Fault and Display the same, if any Call CONVERT_MANUAL_COUNT_TO_HZ to Convert the Potentiometer Setting to the Required Motor Speed in Hz and to Set the Modulation Index No Is 1 sec time interval over? Yes Call RAMP_SPEED to Accelerate/ Decelerate the Motor Call CALCULATE_UPDATE_STEP_SIZE to Find Vector Update Step Size based on the Motor Speed DS00955A-page 10 © 2005 Microchip Technology Inc. AN955 FIGURE 8: SVM IMPLEMENTATION FLOWCHART (INTERRUPT SERVICE ROUTINES) High Priority Interrupt Service Routine ISR_HIGH No Is PTIF = 1? Yes Vector Angle = Vector Angle + Vector Update Step Size No Is carry generated? Yes Increment Sector Number by 1 No Is Sector Number > 5? Yes Reset Sector Number to 0 Calculate TA, TB, T0/2 and (TS – T0/2) using the Vector Angle Load PWM Duty Cycle Registers as per Table 2 RETFIE Low Priority Interrupt Service Routine ISR_LOW No Is ADIF = 1? Yes Read Phase Currents, IGBT Junction Temperature and the Potentiometer Setting for the Motor Speed Is TMR1IF = 1? No Yes Reload TMR1 for 5 msec Overflow Rate Increment RAMP_COUNT by 1 (used for giving 1 sec time interval for acceleration/deceleration feature) Yes Is SW1/SW2 pressed any time? No Toggle LEDs RETFIE © 2005 Microchip Technology Inc. DS00955A-page 11 AN955 TABLE 3: USER-DEFINED PARAMETERS IN SVM FIRMWARE Name Description CHANGE_OVER_DELAY Defines rotation direction changeover for the motor. Its value equals the required changeover time in ms per 39 ms. DIRECTION_AT_POR Defines default rotation direction at start (1 = Forward, 0 = Reverse). CYCLE_COUNT_MAX Defines blinking rate for Fault indication. Its value equals the required blink time interval in ms per 5 ms. MAX_FAULT_CHECK_COUNT Defines time window for Fault recognition. If any Fault occurs for more than predefined count in this time window, then the Fault is recognized and appropriate action is taken. MAX_FLTA_COUNT Defines count for overcurrent Fault recognition. MAX_FLTB_COUNT Defines count for overvoltage Fault recognition. MAX_JUNCTION_TEMP Defines limit for overtemperature Fault. MAX_TEMP_FILT_COUNT Defines count for overtemperature Fault recognition. TMR1L_COUNT and TMR1H_COUNT Defines overflow rate for Timer1. In the present application, it is set for 5 ms. PARAMETER_BUFFER_SIZE Defines array size for storing various compile-time parameters as well as run-time parameters. It is set at 0x35 (do not change this value). TABLE 4: VARIABLES IN SVM FIRMWARE Name Description REQD_SPEED_REF Stores required motor speed set by the potentiometer. SET_SPEED_HZ Stores actual motor speed (Hz). RAMP_COUNT Stores count for Timer1 overflow. It is used for generating 1s time interval as required for acceleration/deceleration feature. CURRENT_R Stores either total DC bus current (when used with DC shunt current measurement) or R phase current (when used with phase current sensor). CURRENT_Y Stores Y phase current (when used with phase current sensor). CURRENT_B Stores B phase current (when used with phase current sensor). JUNCTION_TEMPH Stores junction temperature of the VSI switch. SECTOR_NO Stores present sector location of VS. MODULATION_INDEX Stores required amplitude of VS. VECTOR_ANGLE<MSB:LSB> Stores present vector angle of VS in a sector. TB_COUNT<MSB:LSB> Stores TB count as pointed by the vector angle. TA_COUNT<MSB:LSB> Stores TA count as pointed by the vector angle. HALF_T0_COUNT<MSB:LSB> Stores T0/2 count. TS_MINUS_HALF_T0<MSB:LSB> Stores TS – T0/2 count. TABLE_TB_COUNT<MSB:LSB> Stores array base address for TB count. PARAMETER_BUFFER Stores array base address for compile-time and run-time parameters. DS00955A-page 12 © 2005 Microchip Technology Inc. AN955 TABLE 5: FUNCTIONS IN SVM FIRMWARE Name Description KEY_CHECK Checks the status of Run/Stop (SW1) and Fwd/Rev (SW2) keys. PROCESS_KEY_PRESSED Acts on command issued by the last pressed key. FAULT_CHECK Checks for various Faults (overcurrent, overvoltage, overtemperature) and acts if any Fault is recognized. CONVERT_MANUAL_COUNT_TO_HZ Converts the potentiometer setting into the required motor speed (Hz) and sets the modulation index (m). RAMP_SPEED Implements the acceleration/deceleration feature. CALCULATE_UPDATE_STEP_SIZE Calculates new vector update step size depending on the motor speed. ISR_PWM Responds to setting of PTIF. This routine rotates by vector angle update step size and calculates new duty cycle values for all phases (R, Y and B). ISR_ADC Responds to setting of ADIF. This routine reads the potentiometer setting, phase currents and junction temperature of the VSI switch and stores them at appropriate locations. ISR_TMR1 Responds to setting of TMR1IF. This routine reloads Timer1 for 5 ms overflow rate and increments RAMP_COUNT by 1 for generating a one-second interval (required for the acceleration/deceleration feature). This routine also blinks all LEDs at start when no key is pressed. © 2005 Microchip Technology Inc. DS00955A-page 13 AN955 RESOURCE USAGE CONCLUSION The SVM control application consumes CPU resources, as shown in Table 6. Substantial CPU resources, especially memory and processing time, are still available to users for the development of their own applications. VF control using the SVM in the open loop is more energy efficient compared to the Sine PWM. With an on-chip dedicated motor control peripheral like the power control PWM module and the rich instruction set, the PIC18FXX31 is well suited to give a low-cost solution, implementing the VF control using the SVM algorithm for the 3-phase AC induction motor control. In addition, the on-chip resources, such as the ADC and the multiple timers, allow users to implement other control (acceleration and deceleration) and protection (overcurrent, overvoltage, overtemperature) features. TABLE 6: RESOURCES USED IN THE MOTOR CONTROL DEMO BOARD (USING PIC18F4431) Used Available to User when PIC18F4431 is Used 1942 bytes 14442 bytes Data Memory 93 bytes 675 bytes EEPROM Resource Type Program Memory 44 bytes 212 bytes PWM Channels 6 2 CCP/Fault Input Channels 2 0 ADC Channels 5 4 EUSART 0 1 QEI Module 0 1 Timers 1 3 External Interrupts 0 3 I/O Lines CPU Processing Time (FPWM = 20 kHz, FOSC = 40 MHz) 20 16 ~27% ~63% REFERENCES R. Parekh, AN887, “AC Induction Motor Fundamentals” (DS00887). Microchip Technology Inc., 2003. P. Yedamale, AN843, “Speed Control of 3-Phase Induction Motor Using PIC18 Microcontrollers” (DS00843). Microchip Technology Inc., 2002. R. Parekh, AN889, “VF Control of 3-Phase Induction Motors Using PIC16F7X7 Microcontrollers” (DS00889). Microchip Technology Inc., 2004. “PICDEM™ MC Development Board for PIC18FXX31 User’s Guide” (DS51453). Microchip Technology Inc., 2004. Resource utilization, as mentioned in Table 6, is for a general purpose, relocatable code implementing the VF control using the SVM algorithm on PIC18F4431 with 14-bit PWM resolution. A customized solution with only 8-bit PWM resolution can conceivably result in an additional 10% savings in CPU processing time. DS00955A-page 14 © 2005 Microchip Technology Inc. AN955 APPENDIX A: FIGURE A-1: PICDEM™ MC BOARD TECHNICAL INFORMATION PICDEM™ MC DEVELOPMENT BOARD FUNCTIONAL BLOCK DIAGRAM ICD Connector Potentiometer RS-232 Interface User Push Buttons RS-232 Connector Hall Sensor Connector PIC18FXX31 LEDs Isolated Control Section Quad Encoder Connector Comparator PCPWM Optoisolators Voltage Monitor Current Monitor Phase Current Monitors Temperature Monitor Back EMF Conditioner PCPWM Motor Terminal Block IRAMS10UP60A Gate Driver and 3-Phase Inverter Power Terminal Block VBUS DC AC © 2005 Microchip Technology Inc. Power Switcher +5 VDC +5 VAC +15 VAC D GND A GND Bridge Rectifier DS00955A-page 15 DS00955A-page 16 2 3 1 2 4 3 S3 +5 VD R95 4.7K SW1 (ON/OFF) 1 S4 4 R98 4.7K SW2 (FWD/REV) +5 VD R97 4.7K R96 4.7K FAULTC SW1 SW2 2 RC1 RC0 OSC2 OSC1 CF3 RE2 CF2 RA5 QEB QEA INDX CF1 C52 R25 2.8K R26 4.7K +5 VD RD1 RD0 INT0 FAULTB 0.1 μF 33 pF C19 4.7K R27 R43 100 R44 2K +5 VD 0.1 μF VREF 2K R42 C26 RC7/RX/DT RD4/FLTA RD5 RD6/PWM6 RD7/PWM7 VSS VDD RB0/PWM0 RB1/PWM1 RB2/PWM2 RB3/PWM3 RB4/PWM5 RB5/PWM4 RB6/PGC RB7/PGD 0.1 μF RC4/INT1 RC5/INT2 C17 1 U4:A 0.1 μF MCP6002 8-DIP 4 8 +5 VD 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 3 2 1 RC1 JP1 RD2 RD3 INT1 INT2 TX RX RD4 SW1 SW2 PWM0 PWM1 PWM2 PWM3 PWM5 3 RB6 1 2 JP3 RB7 RD4 +5 VD C53 33 pF R24 1M RD2/SDI/SDA PIC18F4431 RD1/SDO RD0/T0CKI/GPCKI RD3/SCK/SCL RC3/INT0 RC2/CCP1 RC1/T1OSI/CCP2 RC6/TX/CK/SS RC0/T1OSO/T1CKI OSC2/CLKO/RA6 OSC1/CLKI/RA7 VSS VDD RE2/AN8 RE1/AN7 RE0/AN6 RA5/AN5/LVDIN RA4/CAP3 RA3/AN3/VREF+ RA2/AN2/VREF- RA1/AN1 RA0/AN0 U3 R40 470 MCLR/VPP C54 33 pF 3 2 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0.1 μF C25 MCLR RD5 220 μF 25V C21 300 R34 PWM4 0.1 μF C18 +5 VD GND V02 V01 VCC GND V02 V01 VCC TLP2630/ SFH6326 3 CA2 4 AN2 U8 PWM1 PWM0 1 AN1 2 CA1 R39 300 R38 300 GND V02 V01 VCC TLP2630/ SFH6326 3 CA2 4 AN2 U7 PWM3 PWM2 1 AN1 2 CA1 R35 300 U5 PWM5 TLP2630/ SFH6326 3 CA2 4 AN2 1 AN1 2 CA1 R33 300 300 R30 5 6 7 8 5 6 7 8 5 6 7 8 R37 1K R36 1K R31 1K R28 1K LIN1 HIN1 C24 0.1 μF LIN2 HIN2 C23 0.1 μF +5 VA R32 1K LIN3 HIN3 C22 0.1 μF +5 VA R29 1K +5 VA FIGURE A-2: C27 1 3 S2 4 R41 10K RESET +5 VD AN955 BOARD SCHEMATIC, PART 1 (PIC18F4X31 MICROCONTROLLER, PCPWM ISOLATORS, CURRENT COMPARATOR AND ASSOCIATED PARTS) © 2005 Microchip Technology Inc. © 2005 Microchip Technology Inc. OSC1 OSC2 C48 33 pF CF3 HC – 49US INT0 FAULTB RC1 RC0 OSC2 OSC1 QEB Y1 14 13 12 11 10 9 8 7 6 5 QEA 4 3 3 VREF 2 1 2 1 CF1 MCLR RC3 RC2/CCP1 RC1/CCP2 RC0 OSC2/RA6 OSC1/RA7 VSS VDD RA4/AN4 RA3/VREF+ RA2/VREF- RA1/AN1 RA0/AN0 MCLR/RE3 RC6 RC7 VSS VDD PWM0 PWM1 PWM2 PWM3 PWM5 PWM4 RB6 RB7 C49 33 pF RC4/INT1 RC5/INT2 U19 PIC18F2431 15 16 17 18 19 20 21 22 23 24 25 26 27 28 INT1 INT2 TX RX PWM0 PWM1 PWM2 PWM3 PWM5 PWM4 RB6 RB7 C41 0.1 μF +5 VD OPTIONAL JP6 JP5 +5 VD R99 100K TX RD1 RX SW1 SW2 C46 1 μF RX TX C47 1 μF C44 1 μF 6 3 1 9 12 10 11 2 MCP201 LIN 6 VSS 5 4 TXD VBAT 7 3 VDD 2 CS/WAKE 1 RXD FAULT/SLPS 8 U17 RD0 +5 VD 15 5 4 8 13 7 14 16 R100 100K GND C2- C2+ A2IN A1IN VCC MAX232 16-DIP V- C1- C1+ A1OUT A1OUT T2IN T1IN V+ U18 D24 39V +5 VD R107 10 ohm R101 1K J14 PIN1 PIN6 PIN2 PIN7 PIN3 3 PIN8 PIN4 4 PIN9 PIN5 5 2 1 D22 1N4007 +5 VD D23 27V C42 0.1 μF D21 1N4007 50 R106 C43 1 μF C45 1 μF 9 8 7 6 3 2 1 J13 FIGURE A-3: JP9 INDX +5 VD +5 VD AN955 BOARD SCHEMATIC, PART 2 (PIC18F2X31 MICROCONTROLLER SOCKET, USART, CLOCK OSCILLATOR NETWORK AND OPTIONAL LIN INTERFACE) DS00955A-page 17 DS00955A-page 18 J2 5 4 3 2 1 6 5 4 3 2 1 +5 VD +5 VD R16 10K R17 10K +5 VD R15 10K +5 VD QEB RA5 CF1 VREF INDX QEA INT0 INT1 INT2 J7 6 5 4 3 2 ICD 1 J3 5 4 3 2 1 J9 +5 VD R22 10K R21 10K +5 VD +5 VD RB7 RB6 MCLR +5 VD 8 7 6 5 4 3 2 1 10K +5 VD 1K 1K R19 R20 1K R18 PWM3 PWM5 PWM4 RB6 RB7 PWM0 PWM1 PWM2 QEB QEA INDX J10 6 5 4 3 2 1 RD0 RD1 FAULTB INT0 RC0 RC1 J11 10 9 8 7 6 5 4 3 2 1 RC0 RD2 RD1 RD0 470 R105 470 R104 470 R103 470 R102 RD2 RD3 INT1 INT2 TX RX RD4 RD5 SW1 SW2 J12 D20 D19 D18 D17 3 2 1 CF3 RE2 CF2 JP4 FIGURE A-4: R23 J8 AN955 BOARD SCHEMATIC, PART 3 (SENSOR AND MICROCONTROLLER HEADER CONNECTORS, MONITOR LEDS) © 2005 Microchip Technology Inc. © 2005 Microchip Technology Inc. VBUS + LEG3 LEG2 LEG1 560K R88 560K R90 560K R85 R83 560K R80 560K R78 560K R109 100K 560K R91 C34 0.1 μF 560K R86 C33 0.1 μF 560K R81 C32 0.1 μF 560K 560K 560K R55 100K R76 R75 R73 C35 0.1 μF 27K R92 R70 R69 JP2 10K R72 22K 30K R68 30K R89 10K R84 22K R79 22K R74 10K R71 10K +5 VA 22K R87 22K R82 22K R77 R54 100K R67 27K 1M 9 12 13 +IND -IND +INC -INC 1M 10 R65 +INB R64 5 6 1M 11 4 -INB +INA -INA R63 3 2 C36 7 4.7K R62 4.7K 1M R66 U12:D MCP6544 14 +5 VA U12:C MCP6544 8 +5 VA R61 4.7K R60 U12:B MCP6544 +5 VA U12:A MCP6544 1 0.1 μF +5 VA 300 R52 300 R49 300 R48 300 R50 R59 4.7K +5 VA U14 V02 6 GND 5 VCC 8 V01 7 TLP2630/ SFH6326 3 CA2 4 AN2 1 AN1 2 CA1 V02 6 GND 5 3 CA2 4 AN2 TLP2630/ SFH6326 VCC 8 V01 7 1 AN1 2 CA1 U13 R51 1K R53 1K R46 1K C30 0.1 μF +5 VD R47 1K FAULTB C29 0.1 μF +5 VD R113 1K QEA 3 2 1 INT1 INDX 3 2 1 INT0 QEB 3 2 1 INT2 JP10 JP11 JP8 FIGURE A-5: 0.1 μF C31 R56 100K AN955 BOARD SCHEMATIC, PART 4 (SIGNAL CONDITIONER FOR SENSORLESS BLDC OPERATION) DS00955A-page 19 DS00955A-page 20 +15 VA HIN1 HIN2 HIN3 LIN1 LIN2 LIN3 U V W R108 4.3K VBUS+ FUSE 6.3X32 F2 C39 10 μF 16V C38 10 μF 16V C37 10 μF 16V 300 R93 0.05R/3W R110 DC- C56 33 pF ISM SFH618 1 +LED COL 4 2 -LED EMT 3 U16 C57 4.7 nF 1K R111 91K R94 1K +5 VD R112 10K R116 3 2 1K R115 4 8 U11:A MCP6002 8-DIP +5 VA 1 R117 RE2 51K 1% C55 0.1 μF 5 6 7 C58 100 pF U11:B MCP6002 8-DIP R118 360 +5 VA -LED U20 I2 VCC2 N/C N/C LOC111 8-DIP 4 I1 2 +LED 3 VCCT 1 5 6 7 8 7 CF1 JP7 U4:B MCP6002 8-DIP 5 6 R119 51K 1% R120 470 FIGURE A-6: VB3 1 VS3 2 NC 3 VB2 4 VS2 5 NC 6 VB1 7 VS1 8 NC 9 V+ 10 NC 11 DC12 DC13 DC14 H1 15 H2 16 H3 17 L1 18 L2 19 L3 20 ITRIP 21 VCC 22 VSS 23 U15 IRAMS10UP60A AN955 BOARD SCHEMATIC, PART 5 (3-PHASE INVERTER POWER MODULE AND SHUNT CURRENT MEASUREMENT) © 2005 Microchip Technology Inc. R Y B G U V W LEG1 LEG2 LEG3 4 3 2 1 C28 33 pF FAULTC EARTH CF1 2.6K R45 1K R121 D12 1N4448 +5 VD 9 +5V 7 OUT 8 0V LTS15-NP U6 OPTIONAL IN6 6 IN5 5 IN4 4 3 IN3 2 IN2 1 IN1 © 2005 Microchip Technology Inc. CF2 Load R124 0.01R, 1/2W instead of U6 0.1 μF C51 +5 VD 33 μF 35V C50 1K R122 D13 1N4448 9 +5V 7 OUT 8 0V LTS15-NP U9 OPTIONAL IN6 6 IN5 5 IN4 4 3 IN3 2 IN2 1 IN1 Load R125 0.01R, 1/2W instead of U9 CF3 +5 VD 1K R123 D14 1N4448 IN6 6 IN5 5 IN4 4 9 +5V 7 OUT 8 0V LTS15-NP U10 OPTIONAL Load R126 0.01R, 1/2W instead of U10 FIGURE A-7: 3 IN3 2 IN2 1 IN1 J6 AN955 BOARD SCHEMATIC, PART 6 (MOTOR TERMINAL BLOCK AND OPTIONAL CURRENT TRANSDUCER CIRCUITRY) DS00955A-page 21 5 6 C16 RV1 216010 F1 C7 56 pF R12 1.3 ohm DC- U1 1 2 3 4 5 DC- 1N5818 D7 S GND D VCC OCP/FB 4 AC2 3 AC1 2 1 ohm 3W R2 R11 750 ohm R4 150K D8 1N4148 DC- R3 47K DC- R13 2.4K D9 1N4148 C15 R14 2.2 nF 400V 10 ohm DC- 27 ohm R5 D11 1N4937 C2 4.7 μF 400V C12 220 pF C6 1N4148 33 μF 25V R10 4.7K D4 470 μF 250V C5 J17 SHORTING LINK 2 1 470 μF 250V C1 VBUS+ C13 47 pF DC- DC- D1 1 GBPC2506C AC INPUT R1 NTC 0.01 μF 270 VAC DC- 4 EARTH 3 J1 G N L 2 DS00955A-page 22 1 E7 DC- 5 4 9 6 10 7 3 2 8 1 4 U2 1 3 CA 2 A 1 11DQ10 MOC8101 C 5 E D5 R9 1K TL431 L2 0.1 μF C14 L1 C10 47 μF 25V C9 47 μF 25V 10 μH 10 μH C11 100 μF 25V 10 μH L3 C8 100 μF 25V D2 C3 100 μF 25V 11DQ10 D6 11DQ10 D3 6 NC T1 TRANSFORMER TSD-877 E3 R7 4.7K R8 4.7K E5 D10 R6 470 ohm +5 VD E6 +15 VA E4 C4 47 μF 16V +5 VA FIGURE A-8: IRIS4009-HORZ DC- DC+ AN955 BOARD SCHEMATIC, PART 7 (POWER SUPPLY) © 2005 Microchip Technology Inc. AN955 TABLE A-1: SIGNALS USED IN THE PICDEM™ MC SCHEMATIC Signal Name Function +15 VA Non-isolated DC supply voltage for power components. +5 VD Isolated supply voltage for digital components. CF1, CF2 or CF3 Current feedback signal from designated motor phase winding. CF can also represent total motor current when current transducer measurement is used. DC- DC bus return path. FAULTB PCPWM Fault signal input (overvoltage). FAULTC Fault signal input from comparator (overcurrent). HIN1, HIN2 or HIN3 Upper leg input for designated phase to 3-phase inverter (isolated signal). INDX Index position signal to QEI inputs on microcontroller. INT0, INT1 or INT2 Hall effect sensor signal to interrupt-on-change inputs on microcontroller. LEG1, LEG2 or LEG3 Current transducer signal for designated motor winding phase. LIN1, LIN2 or LIN3 Lower leg input for designated phase to 3-phase inverter (isolated signal). MCLR Microcontroller hardware Reset. PWM0 through PWM5 PCPWM waveform outputs from microcontroller. QEA, QEB Quadrature encoder sensor signals to QEI inputs on microcontroller. RAn, RBn, RCn, RDn or REn Bit n of the designated port of the microcontroller. RX and TX RS-232 serial receive and transmit. SW1, SW2 Push button input from designated switch to microcontroller. U, V, W Drive level output from inverter power module to motor. VBUS+ DC high voltage to inverter power module. VREF External reference voltage for overcurrent detect. © 2005 Microchip Technology Inc. DS00955A-page 23 AN955 APPENDIX B: SINE PWM APPENDIX C: The Sine PWM is implemented using a VSI as shown in Figure 2. At any instant, either the top or the bottom switch of a half bridge is on. Hence, the resultant phase-to-virtual neutral point ‘O’ (VRO, VYO and VBO) can be represented as: EQUATION B-1: Vio = VDC × V (where = R, Y, B) if i 2 Vif represents the 3-phase waveforms in space with 120° (2π/3) phase shift between them. Each phase waveform can be represented as shown in Equation B-2: EQUATION B-2: MOTOR CONTROL MADE EASY To assist motor control developers, Microchip has developed the PICDEM™ MC Development Board based on the PIC18FXX31. This demo board has all the necessary hardware for a range of motor control, for example, AC Induction motor, BLDC motor and Stepper motor. Various control algorithms have been developed using the demo board to assist users in developing motor control application. Also, a PC-based GUI has been developed for helping users in configuring different motor control parameters and giving real-time capability to monitor the motor speed, the 3-phase currents and temperature. All source code and the motor control GUI are free to use and can be downloaded from the Microchip web site at: www.microchip.com. VRf = m × sinθ VYf = m × sin(θ + 2π/3) VBf = m × sin(θ + 4π/3) Substituting Equation B-2 into Equation B-1, we get: EQUATION B-3: VDC (m × sinθ) 2 VDC (m × sin(θ + 2π/3)) VYO = 2 VDC (m × sin(θ + 4π/3)) VBO = 2 VRO = The resultant line-to-line output voltage is given as: EQUATION B-4: VRY = VRO – VYO = √3 × VDC × m × sin(θ + π/6) 2 VYB = √3 × VDC × m × sin(θ + (5π)/6) 2 VRB = √3 × VDC × m × sin(θ + 3π/2) 2 From Equation B-4, it is clear that the maximum line-toline voltage in the linear operating range is achieved when m = 1. EQUATION B-5: Maximum line-to-line voltage = √3 × VDC 2 This clearly shows that in Sine PWM, the VDC utilization is less than 90% (~86.6%) in the linear operating range. DS00955A-page 24 © 2005 Microchip Technology Inc. Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property. • Microchip is willing to work with the customer who is concerned about the integrity of their code. • Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as “unbreakable.” Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act. Information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. 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Analog-for-the-Digital Age, Application Maestro, dsPICDEM, dsPICDEM.net, dsPICworks, ECAN, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP, ICEPIC, MPASM, MPLIB, MPLINK, MPSIM, PICkit, PICDEM, PICDEM.net, PICLAB, PICtail, PowerCal, PowerInfo, PowerMate, PowerTool, rfLAB, rfPICDEM, Select Mode, Smart Serial, SmartTel, Total Endurance and WiperLock are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. SQTP is a service mark of Microchip Technology Incorporated in the U.S.A. All other trademarks mentioned herein are property of their respective companies. © 2005, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved. Printed on recycled paper. Microchip received ISO/TS-16949:2002 quality system certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona and Mountain View, California in October 2003. The Company’s quality system processes and procedures are for its PICmicro® 8-bit MCUs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory and analog products. In addition, Microchip’s quality system for the design and manufacture of development systems is ISO 9001:2000 certified. © 2005 Microchip Technology Inc. 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